I would agree with you; commentary on the issue of tax havens would be a very welcome addition to the report. By the very nature of the problem, we don't always have sufficient data to evaluate where the money is going and who is hiding what from whom. Since September 11 there has been some more transparency in the global system, but I still think we have a ways to go.
On the issue of taxation within developing countries, one of the problems is that the kind of policy advice the IMF gives is that they favour value-added taxes, such as our own GST. In my opinion, those are more regressive taxes when we need progressive tax regimes, where the wealthy will pay their fair share.
Here's another area where I'm quite critical of the IMF's advice.